Modular conveying systems are used especially but not exclusively to implement a zero-pressure accumulation or ZPA type conveying. ZPA conveying is used when the loads (parcels) to be transported should not touch each other (because of fragility, accumulation in the curves, etc). The conveying system (also called a conveyor) is then divided into different zones, each of them containing only one load. These zones are all independent and release a load when the following zone is free. In general, each zone integrates its own motor-drive (actuating) and detection system.
Referring now to FIG. 1, a description is provided of a prior-art solution of a modular conveying system, proposed by the firm Interroll. The loads (parcels) are referenced 10. The arrow referenced 4 indicates the conveying direction. In the example of FIG. 1, the conveying system (or conveyor) comprises three modules. Each module has a zone 1, 2 or 3 controlled by the control module 5 (called “ZoneControl”). Each zone has a drive roller 7, a sensor 6, slave rollers 11 (driven in cascade by the drive roller via transmission belts 12). The control devices 5 are connected to one another via connections 9, for example of the P2P (peer-to-peer) bus type, in order to exchange starting signals, each control device 5 communicating firstly with an upstream control device and secondly with a downstream control device (see example of operation here below). Each control device 5 is also connected to a power supply cable 8. Each control device 5 sends a command signal to the actuator 7 of the zone that it controls and receives a presence signal coming from the sensor 6 of the zone that it controls. Each control device 5 comprises means of configuration (in the form of DIP switches) enabling the configuration of the parameters of the conveying function carried out by the controlled zone and especially the conveying speed of the controlled zone, the direction of rotation of the drive roller of the controlled zone, the logic for the ZPA conveying (individual process or group processing (train mode)).
The working of the system of FIG. 1 is for example the following:                the control device of the zone 3 receives a starting signal: it actuates the drive roller 7 of the zone 3 so that the first parcel 10 leaves the zone 3 (and hence the conveyor);        the control device of the zone 2 receives a starting signal coming from the control device of the zone 3. It actuates the driven roller 7 of the zone 2 so that the second parcel 10 passes from the zone 2 to the zone 3;        the control device of the zone 3 receives a starting signal: it actuates the drive roller 7 of the zone 3 so that the second parcel 10 leaves the zone 3 (and hence the conveyor).        
The prior-art solution of modular conveying systems described in detail here above, has several drawbacks, and especially:                the decentralizing of the control is not optimal. Indeed, each control device controls a zone according to the command signals (starting signals) that it receives from one of the two control devices with which it is connected. But each control device is not capable of dynamically adapting the controlling of its zone. The two control devices with which it is connected do not send it information enabling such a dynamic adaptation (there is no information on upstream or downstream sub-sections situated on either side of the controlled zone);        it does not provide for a simple way of making available information on the entire section (for example the conveyor filling rate). To an even greater extent, it does not enable such section information to be communicated out of the section, i.e. to one or more other sections or again to a computerized supervision system (for example of the WCS (warehouse control system), WMS (warehouse management system), control screens, etc) types;        it does not enable the transit, at the same time as the loads are transported from one end to the other of the section, of the tracking information associated with these loads;        in terms of behavior (i.e. of function), it enables the configuration (by DIP switches) of only the parameters of the conveying function carried out by the controlled zone (parameters indicating for example that the conveying function is of the ZPA “step by step” type). There is no choice on the nature of the function: only one function among conveying functions (that can be parameterized) is proposed; no other specific function (for example a order-preparing station function or a labeling station function) is proposed;        it enables the configuration of the conveying speed (overall speed or that of the controlled zone) but it does not enable the control device to adapt set values of operation which are possibly indexed on this conveying speed (for example a set value for declaring a “jamming” type malfunction;        the control devices get installed on a conveying system (or conveyor) already constituted mechanically. In other words, each control device is not pre-assembled with a zone to form a pre-assembled module among a limited number of standard pre-assembled modules. This does not greatly facilitate the migration of a module towards a novel architecture (reutilization, recycling, retrofitting).        